http://www.racewaypark.com/main/classes/safety.html

Be sure to check that snell sticker on you old helmet because NHRA rules for 2008 state that "any car running 14.00 and quicker in the 1/4 mile requires a Snell K98 or 2000 or newer OR SFI 41.1A helmet (see complete list below)". Also a new NHRA rule for '08 requires that "any car running 9.99 or quicker in the 1/4 mile requires an NHRA approved FULL face helmet with visor.

The NHRA 2008 Rule Book Reads as follows for Helmets and Goggles:
As outlined under Class Requirements, drivers in all classes, including motorcycles, must wear a helmet meeting Snell or SFI Specifications. Snell K-98 is acceptable in place of any Snell M-rated helmet.
SFI Spec 31.1A = Snell SA, open-face helmet
SFI Spec 31.2A = Snell SA, full-face helmet
SFI Spec 41.1A = Snell M, open-face helmet
SFI Spec 41.2A = Snell M , full-face helmet

E.T. cars (13.99 or quicker) must use a helmet meeting Snell K98, 2000, 2005, 2007 or SFI 31.1A, 31.2A, 31.1/2005, 41.1A, 41.2A or 41.1/2005 Specs. Drivers in supercharged, front-engine, open-bodied cars and Funny Cars must wear a helmet meeting Snell SA2000, SA2005 or SFI 31.1A, 31.2A, or 31.1/2005 Specs. See Class Requirements.

NHRA Helmet Expiration Dates
Label     Expires     Label     Expires
Snell K98     1/1/2009     SFI 41.1A     1/1/2014
Snell 2000     1/1/2012     SFI 41.2A     1/1/2014
Snell 2005     1/1/2017     SFI 31.1/2005     1/1/2017
Snell 2007     1/1/2019     SFI 41.1/2005     1/1/2017
SFI 31.1A     1/1/2014     SFI 24.1 (JDRL only)     1/1/2015
SFI 31.2A     1/1/2014     SFI 24.1/2005     1/1/2017

Modifications to helmet/shield are prohibited. All hemets must have the appropriate certification sticker affixed inside the helmet.

ALL POWER ADDER RACERS WITH N0N-OEM/FACTORY POWER ADDERS IE:SUPERCHARGERS,TURBOCHARGERS,OR THE USE OF NITROUS. SECTION 1A,PAGE 24 OF THE 2006 NHRA RULEBOOK READS AS FOLLOWS. "10.00(*6.40 1/8 MILE) AND SLOWER; ALL E.T.NON-OEM SUPERCHARGER,NON-OEM TURBOCHARGED, OR NITROUS-EQUIPPED CARS WITH AN OEM OR .024-INCH STEEL FIREWALL: JACKET MEETING SFI SPEC 3.2A/1 MANDATORY.